What is the function of a secondary clarifier in a wastewater treatment plant?

The function of a secondary clarifier in a wastewater treatment plant is to allow activated sludge to settle. After the biological treatment process, where microorganisms break down organic matter, the mixture of treated wastewater and activated sludge enters the secondary clarifier. In this tank, the reduced flow allows gravity to separate the solids, primarily the activated sludge, from the liquid. The settled sludge can then either be returned to the aeration tank to maintain a healthy population of microorganisms or removed as waste, while the clarified effluent moves on for further treatment or discharge.

The secondary clarifier plays a crucial role in ensuring that the effluent leaving the treatment plant is low in suspended solids and organic content, which is necessary for meeting environmental discharge standards. This process enhances the overall efficiency of the wastewater treatment process, contributing to the protection of water quality in receiving waters.